Diacetylenic and other polyacetylenic compounds have been used as recording layers for optical discs and similar information storage devices. However, there is a lack of commercially available economical chemicals needed for their preparations. Propargyl alcohol is the only available industrial chemical with a terminal acetylenic functionality. However, diacetylenic chemicals prepared from propargyl alcohol are so inactive that they are impractical for commercial use in recording media. Accordingly, it is an aim of research to discover chemical processes which can be efficiently and economically effected to provide imageable polyacetylenes and their homopolymers.
The development of a visual image which requires exposure at short wavelengths, excludes the economical and efficient laser imaging, since prior polyacetylene compounds are generally incapable of absorbing energy and undergoing polymerization when exposed to light in wavelengths above about 400 nm. Visual images are those images which are clearly recognizable by the human eye and are characterized by high optical contrast in one or more of the red, green and blue portions of the spectrum. By high optical contrast is meant an optical density difference of at least 1.0 between the maximum density and minimum density portions of the image, where optical density is defined as log.sub.10 (1/transmittance) for transmitted light and log.sub.10 (1/reflectance) for reflected light. Such visual imaging is significantly distinguished from prior data recording where image contrast is relatively low and not easily discernable by the human eye or without high magnification. In several cases laser imaging at wavelengths above 400 nm, based on the thermal color change of the polyacetylenic compound to develop a useful visual image, has been attempted, but it has been found that cumbersome high-output equipment, e.g. argon, metal-vapor or gas lasers and the like are required. Relatively low-output lasers, in the 650-500 nm wavelength range, fail to imprint on either known polyacetylenes or their polymers, particularly in relatively thick layers required to produce useful visual images as opposed to the relatively thin layers needed for digital data recording.
Short wavelength imaging of prior polyacetylenic compounds is also accompanied with several drawbacks and disadvantages, among which is a lack of color stability at the lower color transition temperatures of the thermochromic compound. Also, compounds of significantly greater sensitivity are needed for high definition and contrast in recording data and for production of sharp reproducible images. Accordingly, it is the aim of research, with consideration to cost performance and production efficiency, to provide an organic system most suitable for visual imaging and optical data recording, which is imageable at an output energy in the 650-1500 nm wavelength range characteristic of compact semi-conductor diode lasers or in the short wavelength range characteristic of radiation by UV light, electron beam, .alpha.-particles, X-rays, .gamma.-rays, neutrons, etc.
It is an object of this invention to provide a thermochromic or photochromic compound which answers the above needs and which has increased sensitivity to imaging with a compact semi-conductor laser in a wavelength of at least 400 nm or with short wavelength radiation in the 200 to 350 nm range, by a process which has low cost, high performance and high production efficiency.
Another object of this invention is to provide an economical process capable of producing imageable diacetylenic ethers.
Another object of the invention is to provide a transmitted image by a low cost high efficiency process.
Still another object of the invention is to provide an imageable thermosensitive polyacetylene which is receptive to wavelengths up to about 1500 nm and to a recording film utilizing said polyacetylene.
These and other objects of the invention will become apparent from the following description and disclosure.